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i have also made them for physics 3 and chemistry 3!

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  • Created on: 09-06-10 11:13
Preview of GCSE B3

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Movement in and out of cells
Dissolved substances move by diffusion
Active transport:
Substances are absorbed against a concentration gradient
Requires the use of energy from respiration
Cells can absorb ions from a very dilute solution
Other substances such as sugar and ions can also pass through cell membranes.
Many organ systems are specialised for exchanging materials.
In humans:
The surface area of the lungs is increased by alveoli
The surface area of the small intestine is increased by villi
Breathing system- oxygen from the air can diffuse into the bloodstream
-CO2 can diffuse out of the bloodstream
The lungs are in the thorax and are separated from the abdomen by the diaphragm.
Alveoli provide a large, moist surface area, richly supplied with blood capillaries so that gases can
readily diffuse into and out of the blood.
Villi provide a large surface area with many capillaries to absorb the products of digestion by
diffusion and active transport.
In plants:
CO2 enters leaf cells by diffusion
Most of the water and mineral ions are absorbed by root hair cells
The surface area of the roots is increased by root hairs and the surface area of the leaves is
increased by the flattened shape and internal air spaces.
Plants have stomata to obtain CO2 from the atmosphere
Plants lose water vapour from the surface of their leaves
More rapid in hot, dry and windy conditions.
Mostly through stomata controlled by guard cells
If plants lose water faster than it is replaced by the roots then the stomata can close to
prevent wilting

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The circulation system
The heart pumps blood around the body
Blood flows to the organs through arteries and returns through veins.…read more

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The kidneys
A healthy kidney produces urine by:
Filtering the blood
Reabsorbing all the sugar
Reabsorbing the dissolved ions needed
by the body
Reabsorbing as much water as the body
Releasing urea, excess ions and water
as urine
Sugar and dissolved ions may be actively
absorbed against a concentration gradient
People who suffer from kidney failure may be
treated by using a kidney dialysis machine or a
transplant.…read more

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A donor kidney with the same tissue
type as the recipient
Immunosuppressant drugs- to
suppress the immune system
Dialysis Transplant
Advantages: Advantages:
Readily available Able to have a life
Doesn't require surgery Cheaper
Keeps you alive Keeps you alive
Simpler than transplant Only takes one surgery
Disadvantages: Disadvantages:
Expensive for hospital Chance of death- major surgery
Have to return to hospital every Could be rejected
days Stops working after 9 years
Ruins life Difficult to find a tissue match
Takes a long time…read more

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Micro organisms to make food and drink
Bacteria is used in cheese and yogurt and cheese manufacture
Yeast is used in making bread and alcoholic drinks
Yeast is a single celled organism. The cells have a nucleus, cytoplasm and a membrane surrounded
by a cell wall.
Yeast can respire without oxygen producing CO2 and ethanol- fermentation. In the presence of
oxygen yeast carries out aerobic respiration and produces cO2 and water.…read more

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Industrial fermenters
Micro organisms can be grown in large vessels called fermenters to produce useful products like
Industrial fermenters usually have:
An air supply to provide oxygen for aerobic respiration
A stirrer to keep the micro organisms in suspension and maintain an even temperature
A water-cooled jacket to remove heat produced by the respiring micro organisms
Instruments to monitor factors e.g. pH and temperature
The antibiotic, penicillin, is made by growing the mould, penicillium, in a fermenter.…read more

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Using micro organisms safely
Microbes can be grown in a culture medium containing carbohydrates as an energy source, mineral
ions and supplementary protein and vitamins. These nutrients are often contained in an agar
medium which can be poured into a Petri dish.…read more


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